A Relationship Between Transition Region Brightenings, Abundances, and Magnetic Topology

Authors
Fletcher, Lindsay; Lopez Fuentes, Marcelo Claudio; Mandrini, Cristina Hemilse; Schmieder, Brigitte; Démoulin, Pascal; Mason, Helen E.; Young, Peter R.; Nitta, Nariaki
Publication Year
2001
Language
English
Format
article
Status
Published version
Description
We present multi-instrument observations of active region (AR) 8048, made between 3 June and 5 June 1997, as part of the SOHO Joint Observing Program 33. This AR has a sigmoid-like global shape and undergoes transient brightenings in both soft X-rays and transition region (TR) lines. We compute a magneto-hydrostatic model of the AR magnetic field, using as boundary condition the photospheric observations of SOHO/MDI. The computed large-scale magnetic field lines show that the large-scale sigmoid is formed by two sets of coronal loops. Shorter loops, associated with the core of the SXT emission, coincide with the loops observed in the hotter CDS lines. These loops reveal a gradient of temperature, from 2 MK at the top to 1 MK at the ends. The field lines most closely matching these hot loops extend along the quasi-separatrix layers (QSLs) of the computed coronal field. The TR brightenings observed with SOHO/CDS can also be associated with the magnetic field topology, both QSL intersections with the photosphere, and places where separatrices issuing from bald patches (sites where field lines coming from the corona are tangent to the photosphere) intersect the photosphere. There are, furthermore, suggestions that the element abundances measured in the TR may depend on the type of topological structure present. Typically, the TR brightenings associated with QSLs have coronal abundances, while those associated with BP separatrices have abundances closer to photospheric values. We suggest that this difference is due to the location and manner in which magnetic reconnection occurs in two different topological structures.
Fil: Fletcher, Lindsay. Lockheed Martin Solar and Astrophysics Laboratory; Estados Unidos
Fil: Lopez Fuentes, Marcelo Claudio. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Fil: Mandrini, Cristina Hemilse. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Fil: Schmieder, Brigitte. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia
Fil: Démoulin, Pascal. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia
Fil: Mason, Helen E.. University of Cambridge; Reino Unido
Fil: Young, Peter R.. Harvard-Smithsonian Center for Astrophysics; Estados Unidos
Fil: Nitta, Nariaki. Lockheed Martin Solar and Astrophysics Laboratory; Estados Unidos
Subject
EUV BRIGHTENINGS
CORONAL ABUNDANCES
SOLAR MAGNETIC FIELDS
MAGNETIC TOPOLOGY
Astronomía
Ciencias Físicas
CIENCIAS NATURALES Y EXACTAS
Access level
Restricted access
License
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
Repository
CONICET Digital (CONICET)
Institution
Consejo Nacional de Investigaciones Científicas y Técnicas
OAI Identifier
oai:ri.conicet.gov.ar:11336/22488